I've been all the way to 1.85 and back again but no luck I'm currently running 1.775@850 which is solid as a rock.
I've just read the faq's at Abit and one of the suggestions is to reserve IRQ 5 for legacy ISA. I did this and I managed to get in to Windows @900 - 1.850v but then it crashed on a when I tried to run 3DMark 2000. Then It wouldn't get in to windows at all.